Disease relevance of CLC

• Atypically shaped and typical CLC were noted by electron microscopy in the surgical sample from a patient with solid and papillary epithelial neoplasm of the pancreas [1].
• Ultrastructural localization of Charcot-Leyden crystal protein (lysophospholipase) and peroxidase in macrophages, eosinophils, and extracellular matrix of the skin in the hypereosinophilic syndrome [2].
• X-linked nephrolithiasis and engineered deficiencies in some other CLC Cl(-) channels are thought to represent defects of organellar acidification [3].
• After an overview of the general functions of chloride channels, this review will focus on these cloned chloride channels: the CLC chloride channel family, which includes voltage-gated chloride channels, and the cystic fibrosis transmembrane regulator (CFTR), which performs other functions in addition to being a chloride channel [4].
• We recently encountered a case in which Hodgkin's disease and CLC were unexpectedly found [5].

High impact information on CLC

• Three well established structural classes of plasma membrane chloride channels now exist: the ligand-gated chloride channels, the cAMP-stimulated cystic fibrosis transmembrane conductance regulator channel, and the voltage-gated (or swelling-activated) members of the CLC chloride channel family [6].
• A decade of CLC chloride channels: structure, mechanism, and many unsettled questions [7].
• Because the Charcot-Leyden crystal protein, another eosinophil protein, was recently identified in basophils, we tested whether MBP might also be a constituent of blood basophils [8].
• Charcot-Leyden crystals (CLC) are currently believed to be unique to the eosinophil and a hallmark of active eosinophilic inflammation or proliferation [9].
• We must now consider the possibility that the presence of CLC in tissues, sputum, or stool may also represent basophil involvement in disease processes [9].

Chemical compound and disease context of CLC

• CLC were conspicuous by their absence in smears of cysticercosis, although cholesterol crystals were frequently observed [10].
• METHODS: We induced an intravenous water overload of 20 ml/kg body weight in 10 cirrhotics without ascites (CLC), 11 cirrhotics with ascites (DLC), and 10 normal subjects (N) and investigated the relationship of plasma levels of substance P (SP), norepinephrine (NE), and antidiuretic hormone (ADH) to impaired water excretion [11].

Biological context of CLC

• However, A23187 at a concentration (1 microgram/ml) that caused 15% EDN release and 30% CLC protein release also produced release of the cytoplasmic enzyme lactic dehydrogenase (LDH) and loss of cell viability, both of which were calcium dependent [12].
• One of the genes, CLC, was reduced in gene expression and its four exons were sequenced [13].
• Two SNPs (rs374185 and rs384138) were observed in the CLC gene, each with an allele frequency of 68% [13].
• Despite considerable similarity in their amino acid sequences and structural features, the mammalian members of the CLC chloride channel/transporter family have different subcellular locations [14].
• The gene encoding CLC protein was cloned from a chromosome 19-specific library and a fragment overlapping the transcriptional start site was isolated and sequenced [15].

Anatomical context of CLC

• These results indicate that A23187 treatment of eosinophils causes an initial release of membrane-associated CLC protein by a noncytolytic mechanism, and causes degranulation as a result of eosinophil lysis [12].
• The human ClC-4 protein, a member of the CLC chloride channel/transporter family, is localized to the endoplasmic reticulum by its N-terminus [14].
• Mammalian CLC proteins function as Cl(-) channels or as electrogenic Cl(-)/H(+) exchangers and are present in the plasma membrane and intracellular vesicles [16].
• During eosinophilic differentiation of eosinophil-committed cell lines, CLC steady state mRNA levels increase significantly [15].
• With antisera to the purified lysophospholipase, CLC present in vivo in human feces were demonstrated by indirect immunofluorescence to contain eosinophil lysophospholipase [17].

Associations of CLC with chemical compounds

• Mixtures of the MBP and the CLC protein yielded two bands in polyacrylamide gel electrophoresis [18].
• The CLC promoter sequence contains two consensus GATA binding sites, a purine-rich sequence that presents potential binding sites for PU.1, a member of the ets family of genes, as well as sequences described in other myeloid-specific promoters [15].
• Interestingly, the CLC protein demonstrates no affinity for beta-galactosides and binds mannose in a manner very different from those of other related galectins that have been shown to bind lactosamine [19].
• The extracellular release of CLC protein was studied during the degranulation of basophils stimulated by anti-immunoglobulin E (anti-IgE), N-formyl-methionyl-leucyl-phenylalanine (fMLP), phorbol myristate acetate, eosinophil major basic protein (MBP), and calcium ionophore A23187 [20].
• The overall structural fold of CLC protein is highly similar to that of galectins -1 and -2, members of an animal lectin family formerly classified as S-type or S-Lac (soluble lactose-binding) lectins [21].

Other interactions of CLC

• Reverse transcriptase-polymerase chain reaction analyses revealed that undifferentiated HL-60 cells expressed galectin-1, -3, -8, -9, and -10 (identical to Charcot Leyden crystal) mRNAs, and galectin-2, -4, and -7 were negligible before and after the differentiations [22].
• In basophils both the CLC protein positive and the negative granules showed the same characteristic particulate-like structure of the granular matrix and both share the same membrane marker CD63 [23].
• ClC-3, a member of the CLC family of chloride channels and transporters, is expressed in intracellular compartments of neuronal cells and involved in vesicular acidification [24].
• Double-labeling experiments showed, in eosinophils, that CLC protein-containing granules contain also eosinophil peroxidase, a characteristic specific granule protein [23].
• Despite CLC protein having no significant sequence or structural similarities to other lysophospholipase catalytic triad has also been identified within the CLC structure, making it a unique dual-function polypeptide [21].

Analytical, diagnostic and therapeutic context of CLC

• The supernates following centrifugation of cell debris spontaneously formed CLC [18].
• The cDNA clone and complete amino acid sequence data for CLC protein will facilitate structure-function analyses of its unusual hydrophobic properties, unique propensity for crystallization, lysophospholipase, and potential lectin-like activities [25].
• CLC protein was not released into the supernatant during this process as determined by radioimmunoassay [20].
• RESULTS: The crystal structure of the CLC protein has been determined at 1.8 A resolution using X-ray crystallography [21].
• Molecular cloning and characterization of human eosinophil Charcot-Leyden crystal protein (lysophospholipase). Similarities to IgE binding proteins and the S-type animal lectin superfamily [25].

References